The invention discloses an ultrasonic dispersing device and an ultrasonic dispersing method thereof. The ultrasonic dispersing device comprises a dispersing tank, an annular raw material tank and an ultrasonic component, wherein the annular raw material tank is arranged inside the dispersing tank; a gap is formed between the side wall of the annular raw material tank and the inner wall of the dispersing tank; a plurality of dispersing holes are formed in the side wall of the annular raw material tank; an ultrasonic rod of the ultrasonic component is arranged inside the annular raw material tank; the ultrasonic component is used for dispersing a nano material inside the annular raw material tank through ultrasonic waves. The ultrasonic dispersing device is good in dispersion effect.